Damn, so Turtle was wanting to cook all this time??

Chp 8, Vol 11:

“Agrona and Kezess. They seek this insight, don’t they?” As I spoke, a spike pressed against my throat. “Why was I able to gain what other asuras have tried and failed to for so long?”

“Fear.”

I loked at the spikes all around me but did not feel afraid.

“Not your fear. Theirs. Fear has long rooted them in place. Kezess has made himself and his people unchangeable for fear of what change might bring, terror of the beyond. Agrona, in his fear, seeks to change himself at the expense of all others, to burn worlds as fuel for his own ascension. Both are incapable of risk and self-sacrifice, and so they are incapable of gaining new insight.”

I took a step forward, and the spike at my throat receded. Wherever I walked, the spikes unfolded away from me. “But they are the two most powerful beings in this world. What are they both so afraid of? Each other?” The figure unraveled at the edges.

“Focus. That is a story for another time, and unrelated to what you need to accomplish in this moment.”

~ Conversation between Sylvie and the Thing.

So, what do Kezzes and Agrona fear? These "things in the darkness"? Is this the source of the fear that makes Indrath hide his people in another dimension? The fear that made Vritra seek ultimate power?